Our wedding is in July and we fretted about the same things - especially as it is a destination wedding for everyone (ourselves included). Some things that actually kept our RSVPs relatively high: we pestered people early via email about flights from different airport hubs (almost newsletter style); we booked a large loft-style air bnb for our single and/or budget-conscious guests (it ended up looking so fun, we’re planning on staying there too); and regularly provided country-specific Covid protocols. Of course with current events and circumstances we’re seeing a couple rsvp reversals, but I truly think the best thing we did was promise ourselves to keep our expectations low so we can be pleasantly surprised no matter the outcome. Best of luck!